Design and Characterization of Micro-LED Matrix Display With Heterogeneous Integration of GaN and BCD Technologies

Abstract

Micro-light-emitting diodes ( $\mu $ LEDs) are semiconductor devices that have been shown to have higher luminous efficacy, higher contrast ratio, and higher energy efficiency than existing mainstream technologies based on liquid crystals or organic LEDs (OLEDs). Portable display applications such as wearable devices and head-up display are some of the interesting applications of $\mu $ LED displays. However, this technology has not yet been mass-produced for commercial devices due to process yields, costs, and manufacturability issues. This article presents a novel technology for the heterogeneous integration of a $\mu $ LED matrix display with bipolar complementary metal–oxide–semiconductor (CMOS) DMOS (BCD) circuits that could improve manufacturability by eliminating the need for a dedicated bond stack in the bump-bonding process. To validate the concept, custom high-performance, 2-D arrays of parallel-addressed GaN blue $\mu $ LEDs matrices were fabricated. The individual $\mu $ LED pixel diameters are 20 and 50 $\mu \text{m}$ , respectively, and the overall dimension of the array is $650~\mu \text{m}^{2}$ . In addition, a $\mu $ LED display driver-integrated circuit (IC) with a compact size of $3\times 4.4$ mm2 has been designed, implemented, and verified experimentally for the $\mu $ LED matrices. Measured output optical power-forward bias current-forward bias voltage ( ${P}$ – ${I}$ – ${V}$ ) curves of the individual $\mu $ LED pixel are shown. The $4\times 4\,\,\mu $ LED matrix has also been successfully driven using active-matrix driving and display pictures to demonstrate the function of active-matrix driving are presented.